In an OFDM (orthogonal frequency division multiplexing) system, the PAPR (peak-to-average power ratio) is high. Because a signal having a high PAPR tends to cause distortion in a power amplifier, numerous methods have been proposed to reduce the PAPR. One of the proposed methods is PTS (partial transmit sequence), which has a feature of being able to reduce the PAPR without causing signal distortion, making it a preferable method for use in actual systems. PTS is a method whereby a plurality of subcarriers in an OFDM system are divided into a number of groups, and phase rotations are imparted to the subcarrier signals for each group so as to reduce the PAPR. The groups into which the plurality of subcarriers is divided are called segments.
A receiver must acquire the phase rotations that are performed to the subcarrier signals included in each segment in the transmitter. As a method of the transmitter notifying the receiver of the phase rotations, for example, the transmitter transmits a reference symbol having a known phase in each segment, and the receiver estimates the phase rotation of each segment performed by PTS from the displacement of the phase of the reference symbol.
Because phase rotation occurs to the reference symbol in the wireless transmission path from a transmitter to a receiver, the phase rotation amount performed by PTS and the phase rotation amount occurring in the wireless transmission path are included in the phase displacement of the reference symbol. In general, when receiving a signal to which PTS has been applied, it is necessary to acquire the phase rotation amount in response to the time variation of transmission path and the phase rotation amount by PTS.